Structure and method for building a light tunnel for use with imaging devices
View Patent ↗A pixel cell and imager device, and method of forming the same, where the pixel cell has a plurality of metallization and via layers formed over a photosensitive region. The metallization and via layers form a step-like light tunnel structure that augments the photosensitive region's ability to capture light impinging on the photosensitive region.
1. An imager pixel comprising:
a photosensitive region;
a first layer formed over said photosensitive region, said first layer comprising:
first conductive interconnect patterns, a distance between said first conductive interconnect patterns forming a first aperture; and
first interconnect lines, a distance between said first interconnect lines forming a second aperture; and
a second layer formed over said first layer, said second layer comprising:
second conductive interconnect patterns, a distance between said second conductive interconnect patterns forming a third aperture; and
second interconnect lines, a distance between said second interconnect lines forming a fourth aperture,
wherein said first aperture is smaller than said third aperture.
2. An imager pixel as in claim 1 , wherein said third and fourth apertures are wider than said first and second apertures.
3. An imager pixel as in claim 1 , wherein the first aperture is substantially the same width as the photosensitive region.
4. An imager pixel as in claim 1 , further comprising a transparent dielectric layer formed over said photosensitive region and below said first layer.
5. An imager pixel as in claim 4 , further comprising an anti-reflective coating layer formed below said transparent dielectric layer.
6. An imager pixel as in claim 5 , wherein said transparent dielectric layer further comprises metal contact rings.
7. An imager pixel as in claim 1 , further comprising a third layer formed over said second layer, said third layer comprising third conductive interconnect patterns, a distance between said third conductive interconnect patterns forming a fifth aperture.
8. An imager pixel as in claim 7 , wherein said fifth aperture is wider than said third aperture.
9. An imager pixel as in claim 8 , wherein said third conductive interconnect patterns are smaller in width than said second conductive interconnect patterns.
10. An imager pixel as in claim 7 , wherein said first, second, and third layers form a light tunnel comprising a stair-like shape.
11. An imager pixel as in claim 7 , wherein said first, second, and third layers form a light tunnel having a shape substantially similar to the photosensitive region.
12. An imager pixel as in claim 1 , wherein said first and second layers form a light tunnel comprising a stair-like shape.
13. An imager pixel as in claim 1 , wherein said first and second layers form a light tunnel having a shape substantially similar to the photosensitive region.
14. A pixel cell comprising:
a photosensor formed in a substrate below a top surface of the substrate; and
a light tunnel for guiding light to said photosensor, said light tunnel comprising:
a first transparent dielectric layer formed over said photosensor;
a first metal layer formed over said transparent dielectric layer, a distance between interconnects of said first metal layer forming a first aperture;
a second transparent dielectric layer formed over said first metal layer;
a second metal layer formed over said second transparent dielectric layer, a distance between interconnects of said second metal layer forming a second aperture; and
a third transparent dielectric layer formed over said second metal layer.
15. A pixel cell as in claim 14 , wherein said first aperture is narrower than said second aperture.
16. A pixel cell as in claim 14 , wherein said first aperture is substantially the same width as the photosensor.
17. A pixel cell as in claim 14 , further comprising forming an anti-reflective coating layer below said first transparent dielectric layer.
18. A pixel cell as in claim 17 , wherein said first transparent dielectric layer further comprises metal contact rings.
19. A pixel cell as in claim 14 , further comprising a third metal layer formed over said third transparent dielectric layer.
20. A pixel cell as in claim 19 , further comprising a fourth transparent dielectric layer formed over said third metal layer.
21. A pixel cell as in claim 19 , a distance between interconnects of said third metal layer forming a third aperture, wherein said third aperture is wider than said second aperture.
22. A CMOS imager comprising:
an array of image pixel cells arranged in rows and columns formed over a substrate, each image pixel cell comprising:
a photosensitive region; and
a light tunnel for guiding light to said photosensitive region, wherein said light tunnel further comprises:
a first metallization layer formed over said photosensitive region, said first metallization layer comprising first conductive interconnect patterns, wherein a distance between said first conductive interconnect patterns forms a first aperture; and
a second metallization layer formed over said first metallization layer, said second metallization layer comprising second conductive interconnect patterns, wherein a distance between said second conductive interconnect patterns forms a second aperture.
23. A CMOS imager as in claim 22 , wherein the first aperture is narrower than said second aperture.
24. A CMOS imager as in claim 22 , wherein the first aperture is substantially the same width as the photosensitive region.
25. A CMOS imager as in claim 22 , further comprising forming an anti-reflective coating layer over said photosensitive region and below said first metallization layer.
26. A CMOS imager as in claim 22 , further comprising a third metallization layer formed over said second metallization layer, said third metallization layer comprising third conductive interconnect patterns, wherein a distance between said third conductive interconnect patterns forms a third aperture.
27. A CMOS imager as in claim 26 , wherein said third aperture is wider than said second aperture.
28. A CMOS imager as in claim 27 , wherein said third conductive interconnect patterns are smaller in width than said second conductive interconnect patterns.
29. An imager system comprising:
a processor;
an imaging device electrically coupled to the processor, the imaging device comprising a CMOS pixel array, at least one pixel of the array comprising:
a photosensor formed in a substrate; and
a light tunnel for guiding light to said photosensor, said light tunnel comprising:
a first transparent dielectric layer formed over said photosensor;
a first metal layer formed over said transparent dielectric layer, a distance separating points of said first metal layer forming a first aperture;
a second transparent dielectric layer formed over said first metal layer;
a second metal layer formed over said second transparent dielectric layer, a distance separating points of said second metal layer forming a second aperture; and
a third transparent dielectric layer formed over said second metal layer.
30. A light tunnel structure for use in an imaging device comprising:
a first metal layer including conductive interconnects, a distance separating said conductive interconnects of said first metal layer forming a first aperture;
a first transparent dielectric layer formed over said first metal layer;
a second metal layer including conductive interconnects formed over said first transparent dielectric layer, a distance separating said conductive interconnects of said second metal layer forming a second aperture; and
a second transparent dielectric layer formed over said second metal layer, wherein said second aperture is wider than said first aperture.
31. The light tunnel structure of claim 30 , further comprising:
first interconnect lines formed in said first transparent dielectric layer, a distance separating said first interconnect lines forming a third aperture; and
second interconnect lines formed in said second transparent dielectric layer, a distance separating said second interconnect lines forming a fourth aperture.
32. The light tunnel structure of claim 31 , wherein said fourth aperture is wider than said third aperture.
33. The light tunnel structure of claim 30 , further comprising:
a third metal layer including conductive interconnects, a distance separating said conductive interconnects of said third metal layer forming a third aperture; and
a third transparent dielectric layer formed over said third metal layer.
34. The light tunnel structure of claim 33 , wherein said third aperture is wider than said second aperture.
35. The light tunnel structure of claim 30 , wherein said first and second apertures are arranged to guide and focus light on a photosensitive region.
36. The light tunnel structure of claim 35 , wherein said first aperture is substantially the same width as the photosensitive region.
37. The imager system of claim 29 , wherein the first aperture of the light tunnel is substantially the same width as the photosensor.